This invention relates to an electrically insulating material.
In the prior art, as an insulating material for a circuit board, for example, compositions comprising a liquid polybutadiene and a polyisocyanate compound have been known. Since these are liquid compositions, they have been used, for example, as the so called potting material which is casted on a print board, or as the so called dipping material in which a print board is dipped, and, in general, after completion of these treatments, curing is effected to form an insulating material. Whereas, the electrical insulating material comprising the above composition suffered from inconveniences such as inferior weathering resistance and thermal aging resistance.
Accordingly, in place of the above liquid polybutadiene, it has been proposed to use a hyrogenated product thereof. When such a hydrogenated product of the liquid polybutadiene is used, although weathering resistance of the insulating material obtained can be improved to some extent, the following problems ensue as the result of influence from the skeleton of the polybutadiene which is the starting material of the hydrogenated product. That is, when the polybutadiene has much 1,4-addition type skeleton, the hydrogenated product becomes solid to give no fluidity necessary as the potting material or the dipping material, while when it contains much 1,2-addition type skeleton, the average functionality number becomes smaller due to its polymerization process, and therefore there has been involved the problem that the cured product will flow when heated.